Overload and reverse current relay device.



F. CONRAD. OVERLOAD AND REVERSE CURRENT RELAY DEVICE. APPLICATION FILED 001224, 1906. RENEWED JAN. 25, m9.

Patented Sept. 14, 1909.

2 SHEETS-SHEET 1.

WITNESSES: 34 INVENTOR camm zw FY ATTORNEY F. CONRAD. OVERLOAD AND REVERSE CURRENT RELAY DEVICE. APPLICATION FILED 001224, 1906. RENEWED JAN. 25, 1909.

Patented Sept. 14, 1909,

2 8HEETSSHEET 2.

fig. 4.

WITNESSES: 49m M40 0. 6M

mvmfon UNITED STATES P TEN canon.

FRANK CONRAD, OF SWISSVALE, PENNSYLVANIA, ASSZGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

OVERLOAD AND REVERSE CURRENT RE iAY DEVICE.

Original application filed May 8, 1905, Serial No. 259,388. Divided and this applicatio 1906, Serial No. 340,359.

To all whom it may concern:

lle it known that I, FRANK Comm), a cit-iby the operation of circuit-protective apparatus may be insured when the direction of the drop of potential in the circuit becomes reversed, or when the current traversing the circuit exceeds a predetermined amount, regardless of the voltage or power factor of the circuit.

Relay devices of the general character indicated above ha ve usually cml'iodied means for producing a forccor torque approxima tely proportional to the product of the current, voltage and power factor of the circuit it was intended to protect Such devices have operated imperfectly, because when an undue amount of current traverses a circuit, the voltage and power factor of the circuit may drop considerably and consequently suflicient torque may not be exerted to operate the instrument and trip thecircuitbreakers when it is most necessary that the circnit-breakers be opened. Means have sometimes been embodied in such dei'ices for increasing the torque in proportion to decrease in voltage, but the devices have usually been very complex in structure, and, so far as I am aware, no relay device has. heretofore been constructed regardless of changes both in voltage and in power factor.

The present invention comprises not only means for producing a torque that'is dependent upon the product of the current voltage and power factor of a circuit, but it comprises also a torque-producin' means that is responsive to the amount vo current traversing the circuit, the two torques being normally opposed. Ifthe current traversing the circuit exceeds a predetermined amount,

Specification of Letters Patent.

"power factor (which,

that was operative secondary winding Patented Sept. 14:, 1999.

the torque that is dependentupon the current alone may exceed that which is dependent upon the product.- of current, voltage and as beforeexplained, may be small on account of the decrease in voltage and power factor) by such an amount as to efiect operation of the device and cause the circuit-breaker to open. If, for any reason, the current reverses its direction; that is, if the direction of the drop of potential in the circuit becomes reversed, the two torques act in the same direction, and if the total torque exceeds a predetermined amount, the device will operate and cause the circuit-breaker to open.

Figure 1 of the accompanying illustrates, diagrammatically, bodying my invention. Fig,

drawings a system em- 2 1s a diagram 11 filed Qctober 24, Renewed January 25, 1909. Serial No. 474,153.

of torque curves pertaining to my invention;

Fig: 3 illustrates, diagrammatically, a modified form of the relay device 'of Fig. 1, and Fig. 41 is another diagram of curves that pertain to my invention. f p

i A supply circuit, comprising conductors it, 2 and 3, is protected by means of a circuitbrcaker 4 that is provided with a tripping coil 5, the circuit of which is opened and closed by means of a switch-arm}; that is open-circuit position normally maintained in by means of a spring 7 and is adapted to be moved into engagement with a contact terminal 8 by means of a shaft 10.

On the shaft 10 are mounted movableu'icmbers 11 and 12 of relay devices 1? and .14 that are. mmlitications of the instrument forming the subject-matter of Patent No. 794,395, granted & h Ianufacturiug Company, upon an application filed by me. Each of these devices comprises a U-shaped magnetizable core 15 having pole pieces 16 that embrace the movable members, and a winding 17 that is located upon the yoke of the core, the winding 17 for the device 15 being supplied, from 18 of a transformer 19, with current proportional in amount to that which traverses supply conductor 1, and the winding 17 for the device 14: being in like manner supplied with current proportional in amount to that which traverses the con-. ductor 3, by means of a transformer 21, 'Windin 22 that are also located upon the yokes o the cores 15 are connected in closed circuit with windings 23 which surround reto \Vestinghouse Electric ot the current.

duced portions of the pole pieces formed by recesses 24 cut in the pole faces. As de scribed in the above mentioned patent, these instruments will operate as ammeters, so that torques will be exerted upon the movable members 11 and 12 that will be proportional, respectively, to the squares of the currents traversing conductors 1 and Current 1s also supplied to the winding 23 of the device 13 that IS roportional in amount to the difference of potential existing between the supply conductors 1 and 2, this current being derived from secondary winding 25 of a transformer 26, primary winding 27 of which is connected between the said conductors, and winding 23 of the device ltis in like manner supplied with current proportional in amount to the difference of potential existing between the supply conductors 2 and 3 by means of a transformer 28, primary winding 29 of which is connected etween the said conductors. According to well understood principles, the torques exerted upon the movable members 11 and 12 will then be proportional, respectively, to the currents traversing the windings 17, the voltages impressed on the windings 23, and the cosines' of the phase angles existing between the currents and the electromotive forces. The torques of the instruments, when operating as ammeters, should normally oppose their torques when operating as wattmeters.

The operation of the system may be understood from a consideration of the curves of Fig. 2, in which the abscissae are propor-' tional to the amounts of current traversing a circuit and the ordinates are proportional to the torques exerted upon the conducting disks. A curve A represents the variations in the torque due to variations in the amount of current, and it has approximately the form of a parabola, since the torque varies approximately in proportion to the square Curve W is that of the wattmeter element and, for 100 per cent. power factor, it is approximately a straight line, since the torque of the wattmeter device is approximately proportional to the first power of the current. The two curves cross at a point a; under which conditions the two torques are exactly balanced.

Let it be assumed that to move the switcharm 6 against the force exerted by the springs 7,21 torque is required which is,

equal to that represented by the length of .the ordinate 0-30. When the current travjr ersing the circuit either equals "that represented by the length of the abor exceeds scissaeO-31, the torque exerted meter element will exceed that the wattmeter equal to or in by the amexerted by element by an amount either excess of that represented by the length of the ordinate 0-30, and the switch-arm 6'will then be moved into 'en-- gagementwith the contact terminal 8,.

thereby completing the circuit of the operating magnet winding and causing the circuit-breaker 4 to open. If a current equal to that represented by the length of the abscissa 0-32 traverses the circuit in a direction opposite to the normal direction, the torque exerted by the ammeter element will be represented by the length of ordinate (L33 and the torque exerted by the watt meter element will be represented by the length of the ordinate 04H. These two torques will act in the same direction so that the total torque will be represented by the sum of the ordinates 0-33 and 043-1 and will be equal to the torque represented by the ordinate 03(). If the sum of the torques is equal to or exceeds the length of ordinate 0-30, the switch-arm (i will he moved into engagement with the contact terminal 8, the

operating magnet winding 5 will be energized and the circuit-ln'eakcr 4 will be caused to open. It will be noted that the switclrarm 6 moves into engagement with the contact terminal b whether operated on account of an excessive current. in the supply circuit or on account of a.revcrsal of the direction of the drop of potential, because the direction of the torque of the wattineter mechanism changes when the direction of the drop of potential in the circuit It is evident that the current derived from the'secondary winding 25 of transformer 26 divides at the points 35 and 36, part of it traversing the winding 23 and part the winding 22, the part which trav erses the winding 23 producing a flux which cooperates, as just described, with that produced by the current traversing the winding 17 to exert a torque upon the movable member 11 that is proportional to the amount of energy traversing the circuit. A torque is also exerted upon the movable member 11 which is produced by the fluxes due to the currents in the windings 22 and 23 respectively that are derived from the secondary winding 25 of the transformer 26. However, as the current supplied to the winding 23, from the transformer 26, is opposite in direction to the current supplied to the same winding from the winding 22, acting as a secondary to the winding 17, it does not supplement the main ammeter torque but is opposed to it. Then the amount of current which may traverse the circuit when the direction of the drop of potential is normal without causing the circuit-breakers to open is in excess of that which could traverse the circuit if such a torque were not exerted. When the direction of the drop of potential becomes reversed, the three torques are added, because u the two elements of current in the winding 23 then become of the same direction, and consequently less current may traverse the circuit underthese conditions than if-this the flux produced by instrument, I

- with variations in ing the relay device third torque were not exerted. As it is ordinarily desirable that the ainount of current which may traverse the circuit when the .direction of the drop ofpotential is normal without causing the breakers -to open should be large as compared with the normal current, and that the breakersshould be opened by only a very small amount of current when the direction of the potential'drop is IGVOISBChit is seen that this form of instrument will generally be found most useful as a protective device. In certain cases, however, it desirable to vary these conditions of operation, and to that end- I have provided the yoke of the core of the instrumentshown in Fig. 3. with an additional winding 37 that is connected in series circuit with the secondary winding 25 of the transformer 26. The object of this winding is to neutralize that current in the winding22 which is derived from the secondary winding 25 of the transformer 26.

For the purpose of illustrating the eifect of the winding 37 upon the operation of the have shown curves in Fig. 4:, the ordinates of which are proportional the amount of current traversing a circuit and the abscissae to the resultant that is, to the algebraic sum of the torques exerted by the instrument when operating respectively as a watt-meter and as an ammeter. The curvev A illustrates the variations in the resultant torque with the amount of current traversing a circuit when the direction of the drop .of potential is normal and when an instrument of the forni shown in Fig 1 1s employed. Curve B illustrates thevar at ons n the resultant torque with the yariations n the amount of current traversing a circuit when the direction of the. drop of potential is reversed from its normal directionand when an instrument of the form shown in Fig. 1 is employed. Curve G illustrates the variations in the resultant torque the amount 'of current traversing a circuit. when the direction of the drop of potential is normal and. when an instrument of the form shown in Fig. 3 is employed, and curve D illustrates the variat ons in the resultant torque with variat ons in the amount of current traversing a circuit when the direction of the drop of potential is reversed from its normal direction when an instrument of the form shown in Fig. 3 is employed. 4

' A comparison of curve A with curve C demonstrates that if a neutralizing winding 37 is not employed, the amount of current which may traverse a circuit when the direct-ion of the drop of potential is normal without causto trip the circuit-breakers is considerably greater n amount than the current at which the circuit-breakers circuitmay be found tial is normal will be less,

of which are proportional torque ofthe instrument;

'I have accordingly stood that .the core,

the torque which it is sought to eliminate by means of the compensating winding 37 op-- poses the main torque produced by thein strument operating as direction of the drop of potential is normal, whilethe three elements of torque produced by the instrument are added when the direction of the drop ofpotential is reversed from its normal direction. If the winding 37 is employed, this torque may be eliminated, but. the current which may traverse the circuit when the direction of Y and the current which may traverse the circuit when the direction of the drop of potential is reversed from'its normal direction will-be greater, than if no compensating winding were em ployed. I l V In the practical use of my invention, it may become desirable to provide means-for retarding or damping the movements of the rotatable member in order to prevent operation of an instrumentin a parallel circuit to one which may have become disabled and which is protected by another instrument, and

also in order to prevent sudden overloads or other momentary disturbances in the circuit from causing the circuit-breakers to open. provided the shaft. 10, the rotatable conducting members with a damping device comprising radial vanes. 38, it, of course, being underany other suitable form of damping device may be employed.

While the forms of device's here shown are satisfactorily operative and may be found preferable to other constructions that may be devised, it is to beunderstood that I do not limit myself to these specific forms I" claim as my invention:

which connects a movable conducting member, and netizable core having a yoke and polar faces adjacent to the conducting member, of a magnetizing winding located on the yoke of a second winding located "onthe yoke of the core and'a winding located on the polar extremities of the core and connected in closed circuit with said second said polar extremity winding be- 125 winding,

ing supplied'with a. voltage that is proportional to that of the, su ply circuit.

2.' The combination a movable conducting member an a ma an ammeter when the 1. The combination with a supply circuit,

a mag- Y ith a supply circuit,

netizable' core comprising a yoke and pole 1 pieces having reduced portions adjacent to the conducting member, of a magnetizing winding located on the yoke of the core to which is supplied a currentthat is proportional in amount to the current in the supply circuit, a second winding located on the yoke of the core, and a Winding connected in closed circuit therewith and surrounding the reduced portions of the pole pieces upon which is impressed a voltage that is proportional to that of the supply circuit.

The combination with a movable con ducting member and a magnetizable core con'iprising a yoke and pole pieces adjacent to the conducting member, ot' a magnetizing winding located on the yoke of the core,"a second winding located on the yoke of the core, a winding connected in closed circuit with said second winding and located on the pole pieces, and a third winding located on the yoke of the core in proximity to the second windin 4. The combination with a supply circuit, a movable conducting member and a magnetizab-l'e core comprising a yoke and pole pieces adjacent to the conducting member, of a magnetizing winding located on the yoke of-the core and supplied with current proportional in amount to that traversing the supply circuit, a second winding located on the yoke of the core, a winding located on the pole pieces and connected in closed circuit with said second winding, said pole piece winding beingsupplied with a Volta e that is proportional to that of the supp y circuit, and a third winding located upon the yoke of the core in proximity to the second winding and supplied with current proportional in amount and opposed to that portion of the current traversing the second winding that is derived directly from the supply circuit.

5. The combination with a supply circuit, a movable conducting member and a ma netizable core comprising a yoke and pole pieces having reduced portions adjacent to the conducting member, of a magnetizing winding located on the yoke of the core and supplied with current. proportional in' amount to that traversing the supply circuit, a second winding located on the yoke of the core, a winding surrounding the reduced portions ofthe pole pieces. and connected in closed circuit with said second winding upon which is impresseda voltage that, is proportional to the voltage of the supply circuit, and a third winding located upon the yoke )f the core in proximity to and connected in series the second windin iich supplies tothe pole with the circuit w the current in the piece winding a voltage proportional to that of the supply circuit.

6. The combination with a supply circuit, a movable conducting member, means for retarding the operation of the movable member, and a magnetizable core having a yoke and polar faces adjacent to the conducting member, of a magnetizing winding located on the yoke of the core, a second winding located on the yoke of the core and a windingloca-ted on the polar extremities of the core and connected in closed circuit with said second winding to which a voltage is supplied that is proportional to the voltage of the supply circuit.

7. The combination with a supply circuit, a movable conducting member, means for retarding the operation of the movable member, and a magnetizable core comprising a yoke and pale pieces ducting member, of a magnetizing winding located on the yoke of the. core, a second winding located on the yoke of the core, a winding located on the pole pieces and connected in closed circuit with said second winding, and a third winding located on the yoke of the core in proximity to the second winding.

8. The combination with a supply circuit, a movable member, and a magnetizable core having pole pieces member, of acore winding supplied with currentthat is proportional in amount to supply circuit, an auxiliary core winding, a winding located upon the pole pieces and connected in closed circuit with the auxiliary core winding and receiving a voltage that is proportional to the voltage of the supply circuit.

9. The combination with a supply circuit, a movable member, and a magnetizable core having pole pieces adjacent to the movable member, of a core winding supplied with current that is proportional in amount to the current in thesupply circuit, an auxiliary core winding, a winding located upon the pole pieces and connected in closed circuit with the auxiliary core winding and receiving a voltage that is proportional to the voltage of the supply circuit, and a third core winding located in proximity to the auxiliary core. winding.

In testimony whereof, I have hereunto subscribed my name this 18th day of October,'190 6.

FRANK CONRAD.

Witnesses:

OTTO S. SCHAIRER, BIRNEY HINER adjacent to the con- 

